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Gravitational waves in cubic metric-affine gravity

Sebastian Bahamonde1,2,*, Jorge Gigante Valcarcel3,†, and José M. M. Senovilla4,5

  • *Contact author: sbahamondebeltran@gmail.com
  • †Contact author: jorgevalcarcel@ibs.re.kr
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Phys. Rev. D 114, 024027 – Published 10 July, 2026

DOI: https://doi.org/10.1103/dx64-mmmz

Abstract

We derive new exact gravitational wave solutions with dynamical torsion and nonmetricity tensors in the framework of cubic metric-affine gravity (MAG). For this purpose, we consider the full algebraic classification of the gravitational field in general metric-affine geometries and impose a set of type N conditions on the field strength tensors that implement the kinetics of torsion and nonmetricity in a particular cubic MAG model, recently considered to eliminate ghostly instabilities from the vector and axial sectors of the theory. The new solutions represent pp waves characterized by a metric function that includes the dynamical contributions of the torsion and nonmetricity tensors provided by the field equations of the model. In particular, these quantities induce a scalar polarization mode in the gravitational-wave spectrum, thus offering a distinctive phenomenological signature beyond the ordinary tensor polarization modes of general relativity.

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Phys. Rev. D 114, 024027– Published 10 July, 2026
  • Received 8 February 2026
  • Accepted 29 May 2026
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